1. Field of the Invention
The present invention relates to an instrument for use in the building trades and more particularly to an extension level apparatus for vertically aligning two points on spaced apart horizontal surfaces.
2. Discussion of the Relevant Art
The art abounds with numerous devices used by carpenters in order to expedite their work and make it easier for them to build structures utilizing wood members. In particular numerous devices have been suggested to aid a carpenter in installing door openings and mounting doors in a vertical wall. Many devices including a conventional carpenter's level assist the carpenter in determining the vertical position of a particular beam and/or to determine the horizontal portions of other beams. The accuracy of the conventional carpenter's level may be increased, as is well known, by extending the length of the level utilized together with known site glasses.
In particular, U.S. Pat. No. 2,551,524 issued to Bullivant on May 1, 1951 discloses an apparatus in which a carpenter's level may be extended over various lengths in order to increase its accuracy without increasing its physical size when collapsed for storage purposes.
U.S. Pat. No. 3,277,579 issued to Murphy on Oct. 11, 1966 attempts to solve the vertical alignment problem by providing an extension mechanism suitable for determining the location of two points on spaced horizontal surfaces with some degree of accuracy specifically for the purpose of installing partitions, or the like, and which may also be readily adapted for use in fixing the vertical edge door jambs so that they would be in proper alignment and spaced as required.
However, the aforementioned devices and other known mechanisms have the shortcoming of requiring the carpenter using the device to maintain one hand on the apparatus while attempting to shim or adjust the vertical member being installed in order to obtain true vertical accuracy. The device, as disclosed in the patent to Murphy U.S. Pat. No. 3,277,579, provides for the marking of the ceiling and floor utilizing the edge of the device, however, it is impossible to have flush alongside thereto a vertical beam, since there are outwardly extending protrusions which make it unsuitable for applications which require contact with the device and the beam being installed.
Therefore, it is an object of the present invention to provide a vertical extension level which is capable of providing lines or reference marks accurately positioned and in vertical alignment on spaced apart horizontal surfaces, such as a ceiling and floor.
It is another object of the present invention to provide an extension level suitable for determining the vertical position of a beam while being in intimate contact therewith.
It is yet another object of the present invention to provide an extension level apparatus capable of being self-retained within a door opening of a plurality of door heights.
It is still yet another object of the present invention to provide a reliable, accurate level apparatus suitable for use in determining the vertical as well as horizontal jamp members of a door being installed, permitting a carpenter to have both hands free for adjusting and/or shimming the vertical jamb members.
It is still yet another object of the present invention to provide an accurate, reliable apparatus suitable for use with a standard carpenter's level which permits a carpenter to rapidly install a door in a vertical wall.